1. Field
Example embodiments described herein relate to a flat image display apparatus and a method for driving the apparatus. Particularly, example embodiments described herein relate to an image display apparatus including electron-emitting devices and a method for driving the apparatus.
2. Description of the Related Art
It is known to provide a flat image display apparatus to display an image by applying an electron beam emitted from an electron source provided on a flat substrate to a phosphor on an opposite substrate to cause the phosphor to emit light. In such an image display apparatus, the inside of a vacuum container accommodating the electron source and the phosphor should be kept in a high-vacuum state. This is because, if gas is generated and pressure rises in the vacuum container, the electron source can be detrimentally affected, and the amount of emitted electrons can be reduced, although these conditions can vary depending on the type of gas employed.
In order to mitigate such conditions, Japanese Patent Laid-Open No. 4-12436 suggests a configuration having a gate electrode made of a getter material to absorb generated gas.
A getter can be classified into an evaporative type getter and a non-evaporative type getter. Some types of gases are easily absorbed by a getter and other types of gases are not easily absorbed by a getter. The exhaust velocity of the evaporative type getter is very high with respect to water and oxygen, but is very low with respect to an inert gas, such as argon (Ar). Also, the exhaust velocity of the non-evaporative type getter is very low with respect to an inert gas, such as argon.
Typically, when an orbit of electrons emitted from an electron-emitting device is straight toward an opposite electrode, an inert gas such as Ar existing in space is ionized by collision due to the emitted electrons. Inert gas ions generated through the ionization have positive monovalent or multivalent charge, and are accelerated in a direction opposite to that of electrons accelerated by an electric field, and collide with a substrate provided with an electron source (just under an inert gas ion generating unit with high energy). That is, after electrons emitted from an electron-emitting device have passed over the electron-emitting device, accelerated inert gas ions generated through ionization collide with an electron-emitting device existing immediately below, and damage the electron-emitting device. In some cases, discharge may be caused inside and the apparatus may become broken.
In view of such circumstances, Japanese Patent Laid-Open No. 5-121012 suggests a configuration in which an ion pump is externally attached to a main body of a vacuum container of a flat image display apparatus.
U.S. Pat. No. 6,107,745 suggests a configuration including inert-gas-ionizing electron-emitting devices having a sacrificial area provided outside of an image display area of a panel. Electrons are emitted from the electron-emitting devices during a period when no image is displayed.
Japanese Patent Laid-Open No. 2006-127781 suggests a configuration for deflecting electrons emitted from electron-emitting devices from just above the electron-emitting devices, and capturing an inert gas.
Furthermore, U.S. Pat. No. 6,459,209 suggests a configuration of ionizing and exhausting an inert gas with the use of electron-emitting devices in an image display area by raising an anode voltage to 50% of the voltage for displaying an image and maintaining the raised voltage.